The invention relates to a glass that is particularly suitable for use as a primary packaging material in the pharmaceutical industry. Such glasses are subject of high demands with respect to the chemical resistance. In addition the glasses shall be delamination-free, i.e. in use there shall not delaminate any layers from the glass that would contaminate the packaged pharmaceutical agent.
Apart from the very good chemical resistance those glasses that are suitable as primary packaging material in the pharmaceutical industry are subject of further demands, however.
Thus, the glass must be producible in common melting devices, i.e. the viscosity of the melt must be not too high—if possible, the working temperature (temperature at which the viscosity is 104 dPas, also designated as VA or T4) shall not exceed the maximum value of 1350° C. T4 for an energy saving production should be as low as possible.
In addition, the glasses should preferably be free of boron oxide. The EU (European Union) recently has regarded boric acid, diborontrioxide, disodiumtetraborate anhydride, disodiumtetraborate-decahydrate and disodiumtetraborate-pentahydrate as toxic during production. This leads to the consequence that during manufacture particular boundary conditions must be fulfilled and respectively particular precautionary measures must be taken when using such raw materials.
Due to the relatively high costs of boron-containing raw materials, the foreseeable shortages in suitable qualities, as well as the current discussion with respect to reassessments of the toxicity of boron compounds, boron-free glasses are of interest.
Finally the glass should preferably be chemically pre-stressable. In the chemical pre-stressing a particular part of the sodium ions are replaced by potassium ions which, due to the larger potassium ions, lead to a compression stress within the glass. To allow for an effective chemical pre-stressing several boundary conditions must be fulfilled.
From U.S. Pat. No. 8,753,994 B2 and from DE 20 2012 013 126 U1 aluminum silicate glasses are known that shall have an improved chemical resistance. The SiO2 content is between 70 and 78 mol-%, the Al2O3 content is between 4 and 9 mol-%, the MgO content is between 0 and 7 mol-%, and the CaO content is between 0 and 6 mol-%. However, in practice the hydrolytical resistance of these glasses is not sufficient.
The RO 83460 A discloses an aluminum silicate glass having a SiO2 content of 70 to 73 wt.-%, an Al2O3 content of 3 to 6 wt.-%, a CaO content of 3 to 9 wt.-%, with partial additions of BaO up to 2 wt.-%, and a Na2O content of 11 to 14 wt-%, partially with small additions of K2O.
The chemical resistance of this glass is not sufficient.
From EP 2 876 092 A1 a pharmaceutical glass with 50 to 80 mol-% of SiO2, 5-30 mol-% Al2O3, 0-2 mol-% Li2O and 5-25 mol-% Na2O is known. However in this document there are no statements with respect to chemical resistance. However, it must be assumed that it is relatively bad.
From WO 2014/196655 A1 a further pharmaceutical glass is known comprising 69 to 81 mol-% of SiO2, 4 to 12 mol-% Al2O3, 0 to 5 mol-% B2O3, a total alkali content of 5 to 20 mol-%, 0.1 to 12 mol-% Li2O, and a total content of MgO+CaO+SrO+BaO from 0 to 10 mol-%.
Although these glasses have a very low working temperature they must be seen as not sufficiently chemically resistant.
From DE 10 2013 114 225 A1 a chemically pre-stressable glass is known comprising 56-70 mol-% of SiO2, 10.5 to 16 mol-% of Al2O3, 10-15 mol-% of Na2O, and optional additions of B2O3, P2O5, K2O, MgO, ZnO, TiO2, SnO2, as well as 0.001-5 mol-% F. Due to its chemical composition this glass presumably does not have a sufficient chemical resistance.
From DE 10 2009 051 852 B4 finally a boron-oxide-free neutral glass is known comprising 65-72 wt.-% of SiO2, 11-17 wt.-% of Al2O3, 2-8 wt.-% of Na2O, 3-8 wt.-% of MgO 4-12 wt.-% of CaO and 0-10 wt.-% ZnO, wherein the weight ratio CaO/MgO is between 1.4 and 1.8, and a good chemical resistance prevails.
However these glasses are not optimized with respect to a good chemical pre-stressing. In addition, the working temperature is too high. Also the crystallization behavior is problematic due to the low content of network modifiers.